If I recall correctly, the IPCC used a similar system for climatology predictions. It worked well there, too.
[Edit: To be precise: by writing the conclusions of their report using specified English-language terminology to express degrees of certainty, they were able to write a rhetorically-compelling account that incorporated quantitative probability data. The quality of these data is irrelevant to the example.]
If I recall correctly, the IPCC used a similar system for climatology predictions. It worked well there, too.
[Edit: To be precise: by writing the conclusions of their report using specified English-language terminology to express degrees of certainty, they were able to write a rhetorically-compelling account that incorporated quantitative probability data. The quality of these data is irrelevant to the example.]